Laravel Form Request Validation rule "required" not working with null values

I have Laravel/Vue application and I'm submiting form with file and some other data using axios.

  this.loading = true;
  this.errors = {};

  let formData = new FormData();

  formData.append('type', this.type);
  formData.append('file', this.file);
  formData.append('date', this.date);

  axios.post(`/file-upload`,
      formData,
      {
        headers: {
          'Content-Type': 'multipart/form-data'
        }
      })
      .then((response) => {
        if (response.status === 200) {
          this.loading = false;
          // Success..
        }
      })
      .catch((error) => {
        this.loading = false;
        if (error.response.status === 422) { // Laravel XHR Requests errors
          this.errors = error.response.data.errors;
        } else {
          console.log(error);
        }
      });

In Laravel controller I have store method with form request validator

public function store(ImportRequest $request)
{
   // Request is valid..
}

ImportRequest

public function rules()
{
    return [
        'type' => 'required',
        'file' => 'required|mimes:xls,xlsx|file|max:512',
        'date' => 'required|date',
    ];
}

In my vue component default field values is null. And when I submitting empty form I'm expecting that validation will fail and return messages that fields are required but only errors I get is about file mimes, size and date. Nothing about required...

Request Headers Form Data

From Laravel documentation I understand that required rule must return error. "A field is considered "empty" if one of the following conditions are true: The value is null..." https://laravel.com/docs/8.x/validation#rule-required

For now only solution I think of is in javascript check values against null and only if not null add to FormData. In that case required rule works as I expect

Any ideas? Em I doing something wrong?

UPDATED | SOLVED

null is considered as string "null"